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AI-GEOSTATS: SUM: kriging and groundwater chemistry

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  • Oliver Sonnentag
    hello list, following is the summary on my question from April 19. The quesiont was: hello list, i have the following question regarding kriging and
    Message 1 of 1 , May 13, 2003
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      hello list,
      following is the summary on my question from April 19. The
      quesiont was:

      hello list,
      i have the following question regarding kriging and groundwater
      chemistry.
      i'm a grad student in GIS and i've chosen a topic
      dealing with the interpolation of parameters for groundwater
      chemistry by kriging (approx 3000 observation wells). i got tons of
      additional data (landuse, hydrology, geology, soil parameters,
      DGM , etc.....) and i'm looking for a kriging technique supporting
      additional information (qualitative: landuse and aquifers as well as
      quantitative: certain soil paramters, infiltration rate, etc). at first i
      was thinking about Bayes-Markov-Kriging and/ or Simple Updating-
      Kriging and finally compare the results of these with the results of
      simulation. now after almost three weeks of intensive literature
      review (Bardossy (Simple Updating), Goovaerts (Simple with
      varying mean, Cokriging), Pebesma (Ordinary block), Lehmann
      (Bayes-Markov and others), etc.....all dealing with kriging of
      groundwater chemistry supporting additional information or kriging
      of other z-values supporting additional information) and playing
      around with some programs checking out their suitability and
      capabilities (GSTAT, GSLIB, VarioWin, Geostatistical Analyst for
      ArcInfo 8.2, SURFER 8) I'm a little bit confused about the
      appropriate kriging technique and the program(s) to accomplish
      this task. ...............
      as a first step I want to analyse the data to distinct "real" outliers
      that have to be removed from areas with exceptional high values
      that shouldn't be removed (rather find the (hydro)geological sources
      for their existence). as the data comes in ESRI's shape format I
      really appreciated the interactive capabilites when testing their
      Geostatistical Analyst for ArcInfo 8.2 (histogram, qq-plots, voronoi,
      trend analysis, etc.) in combination with Moving Windows statistics
      in ArcView 3.x and CrimeStat for some summary statistics (Moran
      , Geary...)
      the Geostat Analyst also offers an interactive environment for
      finding a suitable model variogram based on the experimental one
      as well as several kriging techniques and crossvalidation. I'm still
      not sure if these would be sufficient (in this case I was thinking
      about Cokriging to handle the additional information as done by
      Goovaerts for precipitation). Has anyone out there some
      experiences with the GA (and cokriging with the second variable
      being influential groundwater chemistry determining factors)?
      working with gstat under W2K (or Linux....i got both running) would
      have the advantages of being able to import/ export ASCIIgrid from
      ArcInfo (running under W2K, that's whay I installed the Windows
      verision of Gstat too) and do the simulation for comparison.
      as this is a MSc thesis (limited time) and I have to mainly focus
      on how to combine the most influental factors on groundwater
      chemistry as additional
      information for kriging, i don't have the time to focus on writing or
      adapting routines (especially when considering my rudimentary
      programming skills). so i'm looking for (an) existing program(s) to
      support my results (the aforementioned appropriate groundwater
      chemistry determing factors) with examples... which kriging
      technique(s) and simulation technique(s) would be appropriate?
      which of the aforementioned porgrams would be the best ("best" for
      allowing quantitive and qualitative additional information for the
      chosen kriging technique) option?

      the three answers were (thanx alot to all of 'em!!!):

      Hi I have not used geostatistics as you but.

      I have applied Ordinary kriging in Idrisi 32 and ArcInfo geostatistical
      Analyst.

      Idrisi 32 provides a front end to Gstat with 3 modules and different
      interfaces. Idrisi has a special option for inputing esri data formats.

      ArcInfo had the same capabilities but I found it easier, with better
      visualizing techniques, better tools for outputing the results
      (perspective display ArcScene, 3d analyst etc.)But it takes only
      integer
      values in the angles when you create the variograms while Idrisi
      accepts
      decimals as well

      I do not know exactly about cokriging etc but as far as ordinary
      kriging
      the capabilities were almost the same but I suggest ArcInfo as the
      wizard guides you and give you more options.

      I hope this help.

      Regards


      Hi,

      Other references are those by Bob Hoeksema at Calvin College.
      He has
      cokriging software
      for modeling groundwater elevation, where surface elevation is a
      covariate,
      and he developed
      a program that implements an algorithm he and Peter Kitinidis
      developed. You can probably do
      something similar with Gstat. I'm sure others will discourage you
      from
      using Arc-Info, at
      least for semivariogram modeling. A maximum likelihood program
      for
      estimating semivariogram parameters is better.

      Good luck

      Yetta


      Oliver,
      My MSc. thesis orientator forwarded your mail to me.
      I am Chemical Engineer and I am working with groundwater, here in
      Porto Alegre, Brazil.
      I have only 170 monitoring wells with water table height values. I
      will sample all or only some of them, looking for hydrochemical
      parameters and then, apply kriging and cokriging for the water
      table, and yet I have not decided wich technique to use with the
      hydrochemical data, since I don't have it already.
      I think that indicator kriging is a helpful tool when trying to use the
      data in categories.
      I work with GSLIB and with Variowin. Also using Surfer 8 and
      AutoCad 2000. Variowin, is only for 2D analysis. GSLIB is the
      software used here in Porto Alegre, and I like it. I don't know if
      you're going to work in 2D or 3D.
      About outliers..
      I am a beginer in this subject, but I think that it is important for you
      to look to your data set, in a GSLIB locmap. Then, there you will
      see outliers, and see if they are outliers in the "neigborhood" being
      considerated. If it is so, you can try to use the outlier, omit some of
      the known data in the neigborhood, and interpolate using kriging.
      Then, put it back again and repeat the routine. It might be helpful. If
      not, it is a matter of decision, to use an outlier and obtain
      overestimated values or maybe the other way.



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